EP1913721A1

EP1913721A1 - Wireless communication system and method

Info

Publication number: EP1913721A1
Application number: EP06765385A
Authority: EP
Inventors: Timothy Spracklen
Original assignee: Pact Engineering (scotland) Ltd
Current assignee: Pact Engineering (scotland) Ltd
Priority date: 2005-08-12
Filing date: 2006-08-11
Publication date: 2008-04-23
Also published as: GB0516589D0; WO2007020475A1; AU2006281200A1; CA2618914A1; NO20081271L

Abstract

A wireless communication system (100), suitable for controlling a down- hole vehicle (105) remotely, comprises a vehicle mounted wireless transceiver (115) and an wireless transceiver (110) associated with a base station (104). A wireless communications channel operates between the transceivers (110,115) via electrically conducting infrastructure of a pipeline (102). A processor (120) at either of the transceivers (110,115) determines an available bandwidth of the wireless communications channel based upon a metric indicative of the quality of the channel. The processor (120) varies a rate of data transfer over the channel in response to the value of the metric. To be accompanied when published by Figure 1 of the drawings.

Description

TITLE OF THE INVENTION

WIRELESS COMMUNICATION SYSTEM AND METHOD

TECHNICAL FIELD This invention relates to a wireless communication system and method. More particularly but not exclusively the invention relates to a wireless communication system and method suitable for remotely controlling a vehicle, or a device. Even more particularly but not exclusively the invention relates to a wireless communication system and method suitable for the remote control and monitoring of a pipeline pig travelling in a pipeline, or a conduit and being remote from their point of launch into the pipeline, or conduit

TECHNICAL BACKGROUND Conventionally, non-destructive inspection, intervention and cleaning apparatus are transported through a pipeline or other conduit using a pipeline device generally referred to as a pipeline pig or crawler.

Pipeline pigs in which an integral generator is powered by fluid flow past the pig, thereby making the use of an externa! power cable to the pig redundant are known in the art. Such pipeline pigs comprise propellers which propel the pigs along the pipelines using the flow of liquid or gas in the pipe to turn the propeller. Therefore there is no direct cable connection from the monitor/controller to the pipeline pigs. The data acquired during the inspection of the pipe must either be stored on board the pig until the pig is recovered from the pipe, or transmitted back along a cable to a terminal.

Each of these approaches has distinct problems associated with it, for example recovering data only when the pig is removed from the pipe prevents the real time analysis of telemetry data by an operator. Such real time analysis is often useful, particularly in drilling operations, where telemetry information can be used to limit or prevent failures of pipe borne apparatus.

it may also be necessary to control the pipeline pig to vary the speed, data monitoring functionality, rate of data etc or monitor the pig to retrieve data collected by the pig or data relating to the pig.

Passing data back along a cable allows real-time data acquisition but maintains the need for a cable between the pig and its base station. This is disadvantageous as the cable can become snagged and does not allow valves etc., to be closed behind the pig. It is also costly to provide such extensive cables.

The need for two way communication between the pig and a location remote from the pig can be accommodated by using the pipeline as the communication channel. The pig can be inductively coupled to the casing or walls of the pipeline to enable the pig to send and/or receive signals. The inductive coupling may also constitute a safety hazard in an oil or gas pipeline.

Systems are known in the art that transmit telemetry data from a probe to a base station via conductive infrastructure of a well. Such systems typically have limited ranges which are insufficient for long pipelines upwards of 4 km long. Accordingly, known systems do not provide a long distance, independent diagnostic and inspection device for use in pipelines and drilling environments. Such systems are known to increase the power of a carrier signal in order to overcome low signal to noise ratios, for example up to 2.5kW. This high power transmission of a carrier signal would deplete an on-board power source rapidly thereby limiting the amount of time that a remote unit could remain within a pipeline.

A problem associated with the use of electrically conductive infrastructure as a signal carrier, such as a metallic pipeline, is that even where conductive joints such as welds are typically impedance mismatched. Such impedance mismatching typically gives rise to signal attenuation and signal reflection that effectively introduces multiple signal paths. This limits the distance over which standard data transmission techniques can operate using conductive infrastructure. A typical current system uses iow frequency carrier waves, for example 2 - 100 Hz, to mitigate the effects of multiple signal paths, this limits the rate of data transmission possible using such a system.

Another problem associated with the use of electrically conductive infrastructure as a signal carrier is that when operating in a non- submerged environment the infrastructure acts as an antenna. This has the effect of decreasing the signal to noise ratio of a signal carried by the infrastructure, due to additive Gaussian white noise. Where the conductive infrastructure is used in a submerged environment, for example underwater, the effects of additive Gaussian white noise on the signal to noise ratio is minimal. However, the infrastructure typicaliy emerges from water at a drilling or production platform. These are very electrically noisy environments for both additive Gaussian white noise due to thee high electrical conductivity of water, particularly salt water and pulse noise, due to drilling and other activities. This has the effect that the signal to noise ratio of signals carried by the infrastructure degrades rapidly once the infrastructure exits the water. There is no control over the signal to noise ratio (SNR), and the greater the distance from the pig to the receiver the greater the SNR. These problems limit the range over which the signal can travel, meaning that the system cannot be used over long lengths of pipeline.

The importance of the signal to noise ratio arises from Shannon's theorems in which it is stated that the maximum data capacity of an ideal data channel is given by:

C = 2B log™ (1 + S/N)

where B is the band width of the channel and S/N is the signal to noise ratio of the channel.

Shannon's theorem shows that a decrease in the signal to noise ratio of a data channel requires an increase in bandwidth to compensate if the channel capacity is to remain constant.

Should the signal to noise ratio fall below a threshold in a conventional data channel, for example a channel employing quadrature phase shift keying (QPSK) the channel will simply 'drop out' and no data transfer will be possible via that particular channel.

Clearly, as the distance between the pig and a data terminal increases the signal to noise ratio will deteriorate impedance mismatches due to an increasing number of joints between sections of pipe that a signal must be transmitted across. Additionally, where the pipe is above ground, the longer the pipe itself the greater the amount of Gaussian additive white noise that is added to the background. Furthermore, current systems allow communication only on a one to one basis, i.e. a single pipeline can carry a signal between a single pig and a single data terminal.

DISCLOSURE OF THE INVENTION

According to a first aspect of the present invention there is provided wireless communication system suitable for controlling a vehicle, or device, control apparatus comprising first and second wireless transceivers having a wireless communications channel operable therebetween, the first transceiver being located upon a vehicle, or device, to be controlled and the second transceiver being located remote from the vehicle, or device,, the wireless communications channel being operable via an electrically conducting infrastructure characterised by a processor associated with either of the first or second transceivers being arranged determine an available bandwidth of the wireless communications channel dependent upon a value of a metric indicative of the quality of the wireless communications channel and being further arranged to vary a rate of data transfer over the wireless communications channel in response to the value of the metric.

Such a system allows for a high data transfer rate to be employed where there is a large available bandwidth, for example where the vehicle, or device, is near to, typically within a few km, a receiving station. Conversely, as the vehicle moves away from the receiving station, for example tens of km, the rate of data transfer is decreased to allow for the attenuation of the signal and increased signal noise. Thus, a usable data channel is maintained over larger distances than can be achieved with current systems. Distance is not the only factor affecting signal to noise ratio and hence the maximum data transfer rate over the data channel. Electrical noise can vary with time, for example production cycles. The system of the present invention can dynamically reconfigure to compensate for changes in the available data capacity of the data channel in response to increases or decreases of noise.

The wireless communications channel may comprise a plurality of carrier frequencies over discrete sub-sets of data are communicated. Each carrier frequency of the plurality of carrier frequencies may be mutually orthogonalised with respect to an adjacent carrier frequency.

Orthogonal frequency division multiplexing (OFDM) of data increases the robustness of a data channel to multipath effects typically caused by impedance mismatches at the junctions between sections of pipe. OFDM also allows the use of high carrier frequencies to be used to transmit data, for example 2.5GHz.

The wireless communications channel may be a spread spectrum communications channel. Data transmitted over the wireless communications channel may be encoded with a pseudo-random digital sequence. The signal to noise ratio of the wireless communications channel is less than unity.

The use of spread spectrum techniques, for example code division multiple access (CDMA), allows a data channel with a very poor signal to noise ratio to be used to carry data. This further allows low power transmissions to be used, typically with a maximum power output of around 2W. The first and second transceivers may be arranged to communicate data therebetween employing both OFDM and CDMA data transfer protocols in combination, via the wireless communications channel.

Such an arrangement combines the advantageous features of both OFDM and CDMA systems.

The second transceiver may be arranged to be inductively coupled to the conducting infrastructure. The second transceiver may be arranged to be inductively coupled to the conducting infrastructure via electrically insulating coupling means.

Inductive coupling of a base station transceiver to, for example, a pipe reduces the chance for the generation of sparks. This is particularly important where the base station in an area with volatile, flammable components in the atmosphere, for example oil or gas platforms.

The processor may be a dynamically configurable processor. A possible configuration of the processor may be selected from a library of possible configurations stored in a memory element associated with the processor, dependent upon the value of the metric. The processor may be a field programmable gate array.

The use of a dynamically programmable processor allows the processing of data sufficiently fast to cope with the demands of software defined radio (SDR) when using OFDM.

The processor may sample a test signal transmitted over the wireless communications channel and received at the respective first or second transceiver in order to determine the value of the metric. The use of a reference signal allows the quality of the communication channel to be ascertained, for example by comparison of the received reference signal to a stored mode! reference signal, for example by means of a bit error rate calculation.

The vehicle, or device, may comprise sensing means arranged to collect sensor data, the processor being arranged to select a portion of the sensor data to be transmitted between the first and second transceivers dependent upon the value of the metric.

The processor may be arranged to store some, or all, of the sensor data upon a local data storage device.

The conducting infrastructure may be in the form of a pipe, a conduit, a rail or any other suitable piece of electrically conductive infrastructure.

A third wireless transceiver remote from both the first and second wireless transceivers and operable to establish a further data communications channel with the first transceiver.

The use of a further base station some distance, typically tens of km, from the first base station increases the range over which the vehicle can operate by maintaining a high quality data channel with the vehicle as it moves away from the first base station.

The second transceiver may be arranged to communicate with a user interface device. The second transceiver and the user interface device may be arranged to communicate via a virtual private network. The user interface device comprises a browser. Content to be displayed upon the browser may be stored on a data storage device local to the vehicle, or device, and is transmitted via the data communications channel to the user interface device.

The use of a secure network connection to transmit data to a browser allows a user to view data acquired by the vehicle, or device, anywhere via a network, typically the Internet. The storage of content at the vehicle, or device, reduces the likelihood of interoperability problems associated with incompatible browsers.

According to a second aspect of the present invention there is provided a method of wireless communication for controlling a vehicle, or a device, comprising the steps of: i) communicating data between first and second wireless transceivers via an element of conducting infrastructure, the first transceiver being associated with a vehicle, or device, to be controlled, or monitored, the second wireless transceiver being remote from the vehicle, or device,; characterised by ii) varying the rate of data communication between the first and second transceivers in response to a metric indicative of the quality of a data communications channel established therebetween.

The method may comprise communicating sub-sets of data via a plurality of carrier frequencies. The method may comprise orthogonalising each carrier frequency with respect to an adjacent carrier frequency.

The method may comprise communicating data between the first and second transceivers using a spread spectrum communications channel. The method may comprise encoding data to be transmitted between the first and second transceivers with a pseudo-random digital sequence. The method may comprise communicating data between the first and second transceivers using both OFDM and CDMA data transfer protocols in combination.

The method may comprise coupling the second transceiver to the conducting infrastructure inductively.

The method may comprise configuring a processor dynamically in order to control the variation of the rate of data communication between the first and second transceivers. The method may comprise selecting an optimised configuration of the processor from a library of possible configurations stored on a data storage device associated with the processor.

The method may comprise establishing a communications channel between the first transceiver and a third transceiver, the third transceiver being remote both the first and second transceivers.

The method may comprise placing the second transceiver and a user interface device in communication via a virtual private network. The method may comprise outputting data at the user interface device via a browser. The method may comprise storing data to be output via the browser at a storage device associated with the vehicle, or device.

According to a third aspect of the present invention there is provided a vehicle, or a device, comprising a wireless transceiver and a processor, the wireless transceiver being arranged to communicate with a remote wireless transceiver characterised in that the processor is arranged to vary the rate of data output via the wireless transceiver in response to a metric indicative of the quality of a communications channel between the wireless transceiver and the remote wireless transceiver.

The wireless transceiver may arranged to employ both OFDM and CDMA data transfer protocols in combination, via the wireless communications channel.

The processor may be a dynamically configurable processor. A possible configuration of the processor may be selected from a library of possible configurations stored in a memory element associated with the processor, dependent upon metric. The processor may be a field programmable gate array.

The processor may sample a test signal transmitted over the wireless communications channel and received at the wireless transceiver in order to determine the value of the metric.

The vehicle, or the device, may comprise sensing means arranged to collect sensor data, the processor being arranged to select a portion of the sensor data to be transmitted between the first and second transceivers dependent upon the value of the metric. The processor may be arranged to store some, or all, of the sensor data upon a local data storage device. Content arranged to be displayed upon a browser at a user interface device may be stored on a data storage device local to the vehicle, or device, and is transmitted selectively via the communications channel to the user interface device.

According to a fourth aspect of the present invention there is provided a dynamically configurable processor arranged to be reconfigured to vary a rate of data transfer via a data communications channel in response to an input indicative of the available bandwidth of the communications channel. The processor may be arranged to derive a metric indicative of the available bandwidth from the input and is further arranged to configure the process dependent upon the value of the metric. A configuration of the processor may be selected from a library of possible configurations stored on a data storage device associated with the processor dependent upon the value of the metric. The processor may be arranged to output data selectively via a wireless transceiver of a vehicle, or device,, the output data being selected dependent upon the available bandwidth of the communications channel.

According to a fifth aspect of the present invention there is provided a method of extending the range of wireless communications between a remote vehicle, or device, and a station comprising varying a rate of data transfer over a communications channel between respective transceivers associated with the vehicle, or device, and the base station in response to a metric indicative of the quality of the communications channel.

The method may comprise establishing a further communications channel with a second base station remote from the vehicle, or device, such that the quality of the communications channel between the second base station and the vehicle, or device, improves in opposition to the quality of the communications channel between the first base station and the vehicle, or device.

DESCRIPTION OF DRAWINGS

Figure l is a schematic diagram of an embodiment of a communications system according to an aspect of the present invention; Figure 2 is a schematic diagram of a vehicle comprising an element of the system of Figure 1 ;

Figure 3 is a schematic diagram of an architecture used in the implementation of software definable radio (SDR);

Figure 4 is a block diagram of a top level design layout of a communication unit of the vehicle of Figure 2;

Figure 5 is a detailed block diagram of the hardware platform of the communication unit of Figure 4;

Figure 6 is a detailed block diagram of the hardware control platform of the hardware platform of Figure 5; and

Figure 7 is flow diagram showing a method of controlling a vehicle according to an aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to Figures 1 and 2, a wireless vehicle control apparatus 100 comprises a pipeline 102, a base station 104 and a remote vehicle 105, typically a pig and may also an autonomous well intervention unit (AWiU), located in the pipeline 102. The base station 104 may be a pipeline pumping station or a well head of an oil or gas production facility.

The pipeline 102 comprises a plurality of sections of pipe 106 connected together by electrically conductive welds 107.

The base station 104 comprises a head assembly 108, a wireless transceiver 110 and an access point PC 112. The wireless transceiver 110 is inductively coupled to the head assembly 108 by insulated wires 114 wrapped about the head assembly 108, typically via an ATEX electrical Zener-barrier. The transceiver 110 communicates with the access point PC 112 either via a wireless or a hardwired network link.

The vehicle 105 comprises a wireless transceiver unit 115, a propeller 116, a dynamo 118, a centra! processor 119, a dynamically configurable processor 120, typically a field programmable gate array (FPGA), a data storage device 122 and a number of sensors 124a-d, typical sensors include temperature and pressure sensors.

The command, control and communications subsystems of the vehicle 105 are implemented in an embedded computing platform on the configurable processor 120,

The flow of fluid past the vehicle 105 rotates the propeller 116 which is coupled to the dynamo 118. The dynamo 118 generates electricity to operate the onboard systems of the vehicle 105, and removes the necessity for an umbilical cord between the vehicle 105 and the base station 104. In alternative embodiments on-board dry cells may be used to power the vehicle 105, either alone, or in combination with the dynamo 118.

The transceiver unit 115 couples to the pipeline 102 inductively via wings 126a,b that project from the vehicle 105. Data acquired by the sensors 124a-d is stored locally upon the data storage device 122.

The pipeline 102 acts as a communications channel between the base station transceiver 110 and the vehicle's transceiver unit 115. As noted hereinbefore such an arrangement has known disadvantages associated with the welds 107 joining the sections of pipe 106, and also with additive Gaussian white noise and shot noise.

The access point PC 112 is connected to the vehicle 105 via a Virtuai Private Network (VPN).

The access point PC 112 is connected to the Internet at the access point to the pipeline 102. The access point PC 112 receives commands from the base station 104 and processes data into a format suitable for connection to the pipeline. A special purpose interface card 126 located in the access point PC takes the processed data and converts it to an appropriate electrical signal for inductive coupling to the pipeline through the wires 114.

In use, the processor 120 monitors the integrity of command sequences it receives, and typically manoeuvres the vehicle 105 within the pipe 102 by executing a complex series of individual commands. Errors in commands sequences are passed back to the access point PC 112 from the vehicle 105 via the communications channel of the pipe 102. Unauthorized, erroneous or dangerous sequences are not accepted and executed by the processor 120.

Typically, frequently utilized command sets are stored on the base station access point PC 112 as html files or cookies which are typically small files, a few tens of kb, and can therefore be quickly transmitted to the vehicle 105. New command sequences can be entered via interactive forms or control panels.

Software at the base station 104 typically based on a standard web browser, for example an Internet web browser such as Microsoft Internet Explorer or Netscape Navigator, is used to control and monitor the progress of the vehicle 105 via the communications link over the pipeline 102.

A user can navigate the vehicle command, control, monitoring and instrumentation subsystems from a graphical user interface (GUI) 128 such as a web page upon the access point PC 112. The user need not be present at the access point PC 112 but may be located at any other PC 130 that is connected to the VPN, typically via the Internet 132. Thus, a user in, for example the UK can monitor the progress of the vehicle in a pipeline in the USA.

The GUI 128 and the vehicle 105 are connected to the VPN through the Access Point PC 128 communications processor card 126 to enable control and/or observation of the vehicle from any Internet access point. The communications processor card 126 provides an interface between the CDMA communications over the pipeline 102 and the VPN.

Any appropriate form of graphical representation of controls can be used within the GUI 128, for example, radio buttons control knobs, cookies, graphics etc. The representations of the controls of the GUI 128 link to control software that allows the control and monitoring of the status of the vehicle's subsystems and sensors 124a-d.

It is possible to have many windows open within the GU1 128. These windows display different webpages simultaneously in order that the user can monitor the status of vehicle 105 while concurrently submitting commands and retrieving data on separate windows or webpages. An advantage of this approach is that new instrumentation can be added to vehicle 105 quickly as no update of the base station software is required. The new subsystem will typically appear as a new webpage within the browser.

Software for generating web pages for controlling the vehicle 105 and displaying the status of the vehicle's subsystems is located in vehicle 105. The scripts for the webpages are typically written in a non-platform specific coding language, such as for example XML. Thus a user only needs access to a web browser in order to be able to control the vehicle 105 and monitor the vehicle's systems and progress. The use of non-platform specific language greatly reduces the likelihood of incompatibility between software at the base station 104 and software at the vehicle 105.

The quality of the communications channel between the vehicle 105 and the base station 104 is monitored regularly. Typically, if the available bandwidth across the channel decreases the user perceives this as a slowing of response times. If the response times become unacceptably high, the processor 120 will automatically close some of the windows. The additional bandwidth freed up by the reduction in data display to a user at the GUI 128 is automatically re assigned to remaining functions. The priority attached to various functions within vehicle 105 facilitates election of windows to be closed, for example a temperature sensor reading may not be regarded as being as important as an indication of remaining battery lifetime.

For example when the vehicle 105 is close, typically less than 10km, to the base station 104 a large amount of data, of the order of 10's of Mbit/s can be communicated between the transceivers. However, as the vehicle 105 moves further away, typically 30km or more, from the base station 104 a small amount of data is communicated between the transceivers as the signal to noise ratio of the channel falls. In some embodiments an additional wireless transceiver 128 is inductively coupled to a section of the pipeline 102 located at a point further away from the base station 104 than the vehicle. Typically, the transceiver 128 operates in the same manner as the base station transceiver 110. The transceiver 128 is typically located 40 to 50 km from the base station and allows the range over which data can usefully be obtained to be extended significantly.

Data from the transmitted by vehicle's transceiver unit 115 is transmitted along the pipeline 102 to the additional wireless transceiver 128.

Typically, data is communicated between the additional wireless transceiver 128 and the access point PC 112 via standard cellular infrastructure and the Internet.

A plurality of additional wireless transceivers may be connected to the pipeline 102 at various locations along the pipeline at appropriate intervals. This enables data from the vehicle 105 to be received or data transmitted to the vehicle irrespective of the distance of the vehicle from the base station. The additional transceivers may be located, for example, at points where the bandwidth available across the communications channel decreases below an acceptable level, for example every 10- 15km. Suitable locations for additional wireiess transceivers may include access points or entry shafts.

If communication to a particular vehicle subsystem fails the programming of the vehicle's processors 119, 120 is such that the vehicle 105 will fail safe and, for example, terminate any possibly damaging commands, such as movement within a confined space where the vehicle 105 may become trapped.

Communication between the vehicle 105 and the base station 104 is typically lost by deliberate user disconnection or by loss of bandwidth.

Instrumentation and monitoring subsystems store data in the data storage device 122, which is typically a non-volatile memory device. In this instance command and contra! systems revert to an autonomous mode where the vehicle 105 is piloted by the processor 119.

The vehicle's transceiver unit 115 monitors the communication channel for beacon data from the base station's transceiver 110. Once the beacon data is detected the vehicle's transceiver unit 115 endeavours re-establish communications upon with the base station's transceiver 110.

The transceiver unit 115 may be arranged to 'power down' such that it resides in a passive 'receive' mode awaiting beacon data as an instruction to transmit data to the base station. Such an arrangement serves to reduce the power consumption of the vehicle 105. This lengthens the amount of time, for example up to 12 months, that the vehicle can remain within the pipeline, this is particularly relevant for embodiments of the invention comprising on-board dry cells to power the on-board electronics.

in normal operating conditions, the vehicle 105 is operated with a flight plan which has been prepared and loaded into data storage unit 122 and the processor 119 in advance. Manual intervention is typically required, for example, when the flight plan must be modified during flight.

Therefore, the communications channel will primarily be used to monitor the progress and status of vehicle 105. The operating system for the monitoring and controlling the vehicle 105 must be suitable for real time environments, reliable and have extensive support for control and data acquisition.

The communications channel between the respective transceivers of the base station 104 and the vehicle 105 employs a protocoi based on CDMA over OFDM.

In Orthogonal Frequency Division Multiplexing (OFDM) a number of sub- carrier frequencies, each being a harmonic of a fundamental, lowest frequency sub-carrier, have complex data values imposed upon them by the use of inverse fast Fourier transform (IFFT) techniques. The complex data values vary the phase and amplitude of the sub-carriers away from their unperturbed state. Upon transmission the carriers superpose to produce a non-sinusoidal signal. When received at a receiver a fast

Fourier transform (FFT) is performed upon the signal to recover the sub- carriers and hence their associated complex data values. OFDM enables data to be sent efficiently, with resilience to interference and lower multi path distortion. The inter symbol transmission period is maintained to be greater than the longest multi path to reduce inter symbol interference.

CDMA is a form of Direct Sequence Spread Spectrum communications enabling data to be sent at, or below, the level of noise in the system.

The main parameter in spread spectrum systems is the processing gain, Gp₁ or spreading factor. This is the ratio of transmission and information bandwidth:

Where: BW_t is the transmission bandwidth

BWi is the information bandwidth

The processing gain determines the number of signals that can be carried within a CDMA system, the amount of muiti path effect reduction, and the difficulty to jam or detect a data transmission. For a spread spectrum system it is advantageous to have a processing gain as high as possible.

There are many different techniques to spread a data, such as direct sequence, frequency hopping, time hopping and multi carrier CDMA. Combinations of these techniques can also be used. The spreading techniques utilised in the present invention typically comprise direct sequence or frequency hopping.

Direct sequence is the best known spread spectrum technique where data is multiplied by a Pseudo Random Noise (PN) code. There is low cross correlation values among the codes so it is difficult to jam or detect a data message.

The generation of PN codes facilitates the introduction of a large processing gain in direct sequence systems, and is known to those skilled in the art.

At the receiver, the data is multiplied again by the same synchronised PN code to extract the original data. The de spread operation is the same as the spread operation.

In order to be useful for direct sequence spreading, a PN code must meet various constraints. These include being built from two levelled numbers, having sharp autocorrelation peak to enable code synchronisation, having a low cross correlation value to allow more users on the system and being balanced for good spectral density properties.

The signal occupies a bandwidth much greater than is necessary to send the information. This results in very low signal to noise channels being usable for the transmission of data using CDMA.

In a system where the pipeline 102 is the communications channel, the channel is typically characterised by a very poor and variable SNR spread spectrum communications can operate effectively.

In CDMA the bandwidth is spread by means of a code that is independent of the data. Typical codes employed in CMDA include Walsh-Hadamard codes, M-sequences, Gold codes and Kasami codes.

The use of a spreading code that is independent of the data and synchronous reception allows multiple data sets to be transmitted across the same frequency band at the same time. The codes used for spreading have low cross correlation values and are unique for each channel of communication. The receiver that has knowledge about code of the intended transmitter is capable of selecting the desired signal.

The data transmission scheme of the apparatus 100 is based upon the concepts of Software Definable Radio (SDR). In SDR a radio frequency (RF) data is digitised as soon as possible, usually after down conversion to a lower Intermediate Frequency (!F), and further processing is handled by software. Such an architecture of SDR 300 is shown schematically in Figure 3 in which an antenna 302 and a tuner 304 are the only analogue elements with an incoming signal being digitised by an ADC 306. The remaining processing of the signal is carried out digitally, either in hardware 308 or software 310.

Due to the high processing power required to process such a digitised OFDM radio signal, an FPGA, for example a Xilinx Vertex series which has a 200MHz clock, is typically used as the intermediate configurable processor 120. FPGAs can implement random access memory (RAM) and the Xilinx Vertex series of FPGAs supports dual port RAM.

An FPGA processor 120 can be configured using supervisor software that is arranged to monitor the quality of the data. The processor and determine whether modification of the configuration of the processor 120 is required to achieve a data transfer rate over the communications channel that is appropriate to both the bandwidth and the signal to noise ratio of the channel.

Figure 4 is a schematic diagram of a design of the communications unit 400 of the vehicle 105. The unit 400 comprises a software platform 402, a hardware platform 404 and an environment interface 406.

The software platform 402 is typically mounted upon the central processor 119 and comprises platform control software 408, a generic pre-processor module 410 and a user interface 412. The software platform 402 is communicates with the hardware platform 404 via a PCI bus 414.

The hardware platform 404 comprises an FPGA 416 module 416 and a hardware control platform 418. The configuration of the FPGA module 416 is controlled by the hardware control platform 418 in response to signals received from the software platform 402 in order to execute the routines necessary for SDR. Software reconfiguration is complex and potentially time consuming as configuration files from the central processor have to be downloaded to the FPGA 416 via the bus structure. Therefore the algorithms that comprise the SDR must be carefully constructed for implementation on hardware. The software reconfiguration strategy approach uses supervisor software responsible for controlling data, configuration and environmental aspects of FPGA 416.

The environment interface 406 comprises a radio frequency interface 420 and a digital to analogue/analogue to digital converter (ADC/DAC) 422. The environment interface 406 provides the interface to the communications channel, typically the pipeline 102. The radio frequency interface 420 receives and transmits signals over the communications channel. The ADC/DAC 422 digitises received signals to allow the FPGA module 416 to carry out SDR functions. Digitised signals to be transmitted are received by the ADC/DAC 422 and are converted to analogue signals for transmission over the communications channel.

Figures 5 is a schematic representation of the hardware platform 404, and Figure 6 is a schematic representation of the hardware control platform 418. The hardware platform 404 comprises a fixed part 424, typically the hardware control platform 418, a reconfigurable part 426 and a reconfiguration logic part 428. The fixed part 424 and the reconfigurable part 426 communicate via an internal bus 440.

The hardware control platform 418 comprises a PCI interface 442, an IO memory buffer 444, an IO port controller 445, an internal bus interface 446, a select map bus interface 448 and an environment interface bus 450. The PCI interface 442 receives communications from the software platform 402 via the PCI bus 414 and communicates the data to either the buffer 444 or the controller 445 as appropriate. The controller 445 communicates with the internal bus interface 446 for transmission of reconfiguration data to the FPGA 416. The controller 445 also communicated with the environment interface bus 450 in relation to received signals from the environment interface 406 and also in relation to signals to be output via the environment interface 406.

The reconfigurable part 426 comprises the FPGA 416 and an internal bus interface 442 for mediating communications between the FPGA 416 and the internal bus interface 440 of the hardware control platform 418.

The PCI bus 414 is used to communicate the desired configuration from the software platform 402. The hardware control platform 418 then requests the appropriate FPGA 416 configuration from the reconfiguration logic part 428 via the select map bus interface 448. The FPGA 416 is configured accordingly dynamically in real time, on the fly.

Although described with reference to a single vehicle located within a pipeline it will be appreciated that the use of OFDM, in particular with CDMA, allows multiple vehicles within a plurality of pipelines to be in communication with a single base station, for example at a manifold. This is because the orthogonalisation and use of multiple frequencies allows individual signals to be filtered out from a number of received signals.

Referring now to Figure 7, a method of controlling a vehicle comprises communicating data between first and second wireless transceivers via a pipeline, the first transceiver being associated with a vehicle to be controlled, the second wireless transceiver being remote from the vehicle {Step 700). The rate of data communication between the first and second transceivers is varied in response to a metric indicative of the quality of a data communications channel established between the first and second wireless transceivers (Step 702).

It will be appreciated that although described with reference to communication between a vehicle and a base station the present invention may be used in communicating between any suitable device and a base station, or other suitable device. For example the present invention may be used in the controi of pipeline valves or well heads on drill strings, the monitoring of remote monitoring stations, and communications via rail lines.

It will be further appreciated that reference "wireless" transceivers and communications channels refers to there being no cable carrying a signal between transceivers.

The invention is not limited to the embodiments herein described which may be varied in construction and detail.

Claims

1. A wireless communication system suitable for remotely controlling a vehicle, or a device, comprising first and second wireless transceivers having a wireless communications channel operable therebetween, the first transceiver being located upon a vehicle, or a device, to be controlled and the second transceiver being located remote from the vehicle, or the device, the wireless communications channel being operable via an electrically conducting infrastructure, characterised by a processor associated with either of the first or second transceivers being arranged determine an available bandwidth of the wireless communications channel dependent upon a value of a metric indicative of the quality of the wireless communications channel and being further arranged to vary a rate of data transfer over the wireless communications channel in response to the value of the metric.

2. A system according to claim 1 wherein the wireless communications channel comprises a plurality of carrier frequencies over discrete sub-sets of data are communicated.

3. A system according to claim 2 wherein each carrier frequency of the plurality of carrier frequencies is mutually orthogonalised with respect to an adjacent carrier frequency.

4. A system according to any preceding claim wherein the wireless communications channel is a spread spectrum communications channel.

5. A system according to any preceding claim wherein data transmitted over the wireless communications channel is encoded with a pseudo-random digital sequence.

6. A system according to any preceding claim wherein the signal to noise ratio of the wireless communications channel is less than unity.

7. A system according to any preceding claim wherein the first and second transceivers are arranged to communicate data therebetween employing both OFDM and CDMA data transfer protocols in combination, via the wireless communications channel.

8. A system according to any preceding claim wherein the second transceiver is arranged to be inductively coupled to the conducting infrastructure.

9. A system according to claim 8 wherein the second transceiver is arranged to be inductively coupled to the conducting infrastructure via eiectricaliy insulating coupling means.

10. A system according to any preceding claim wherein the processor is a dynamically configurable processor.

11. A system according to claim 10 wherein a possible configuration of the processor is selected from a library of possible configurations stored in a memory element associated with the processor, dependent upon the vaiue of the metric.

12. A system according to any preceding claim wherein the processor is a field programmable gate array.

13. A system according to any preceding claim wherein the processor samples a test signal transmitted over the wireless communications channel and received at the respective first or second transceiver in order to determine the value of the metric.

14. A system according to any preceding claim wherein the vehicle, or device, comprises sensing means arranged to collect sensor data, the processor being arranged to select a portion of the sensor data to be transmitted between the first and second transceivers dependent upon the value of the metric.

15. A system according to claim 14 wherein the processor is arranged to store some, or all, of the sensor data upon a local data storage device.

16. A system according to any preceding claim wherein the conducting infrastructure is in the form of a pipe, a conduit, a rail, or any other suitable piece of electrically conducting infrastructure.

17. A system according to any preceding claim comprising a third wireless transceiver remote from both the first and second wireless transceivers and operable to establish a further data communications channel with the first transceiver.

18. A system according to any preceding claim wherein the second transceiver is arranged to communicate with a user interface device.

19. A system according to claim 18 wherein the second transceiver and the user interface device are arranged to communicate via a virtual private network.

20. A system according to either claim 18 or claim 19 wherein the user interface device comprises a browser.

21. A system according to claim 20 wherein content to be displayed upon the browser is stored on a data storage device local to the vehicle, or device, and is transmitted via the data communications channel to the user interface device.

22. A method of wireless communication for remotely controlling a vehicle, or a device, comprising the steps of: i) communicating data between first and second wireless transceivers via an element of conducting infrastructure, the first transceiver being associated with a vehicle, or device, to be controlled, or monitored, the second wireless transceiver being remote from the vehicle, or the device,; characterised by ii) varying the rate of data communication between the first and second transceivers in response to a metric indicative of the quality of a data communications channel established therebetween.

22. The method of claim 21 comprising communicating sub-sets of data via a plurality of carrier frequencies.

23. The method of claim 22 comprising orthogonalising each carrier frequency with respect to an adjacent carrier frequency.

24. The method of any one of claims 21 to 23 comprising communicating data between the first and second transceivers using a spread spectrum communications channel.

25. The method of any one of claims 21 to 24 comprising encoding data to be transmitted between the first and second transceivers with a pseudo-random digital sequence,

26. The method of any one of claims 21 to 25 comprising communicating data between the first and second transceivers using both OFDM and CDMA data transfer protocols in combination.

27. The method of any one of claims 21 to 26 comprising coupling the second transceiver to the conducting infrastructure inductively.

28. The method of any one of claims 21 to 27 comprising configuring a processor dynamically in order to control the variation of the rate of data communication between the first and second transceivers.

29. The method of claim 28 comprising selecting an optimised configuration of the processor from a library of possible configurations stored on a data storage device associated with the processor.

30. The method of any one of claims 21 to 29 comprising establishing a communications channel between the first transceiver and a third transceiver, the third transceiver being remote both the first and second transceivers.

31. The method of any one of claims 21 to 30 comprising placing the second transceiver and a user interface device in communication via a virtual private network.

32. The method of claim 31 comprising outputting data at the user interface device via a browser.

33. The method of claim 33 comprising storing data to be output via the browser at a storage device associated with the vehicle, or device.

34. A vehicle, or a device, comprising a wireless transceiver and a processor, the wireless transceiver being arranged to communicate with a remote wireless transceiver characterised in that the processor is arranged to vary the rate of data output via the wireless transceiver in response to a metric indicative of the quality of a communications channel between the wireless transceiver and the remote wireless transceiver.

35. A vehicle, a device, according to claim 34 wherein the wireless transceiver is arranged to employ both OFDM and CDMA data transfer protocols in combination, via the wireless communications channel.

36. A vehicle, or a device, according to either claim 34 or claim 35 wherein the processor is a dynamically configurable processor.

37. A vehicle, or a device, according to claim 36 wherein a possible configuration of the processor is selected from a library of possible configurations stored in a memory element associated with the processor, dependent upon metric.

38. A vehicle, or a device, according to any one of claims 34 to 37 wherein the processor is a field programmable gate array.

39. A vehicle, or a device, according to any one of claims 34 to 37 wherein the processor samples a test signal transmitted over the wireless communications channel and received at the wireless transceiver in order to determine the value of the metric.

40. A vehicle, or a device, according to any one of claims 34 to 39 wherein the vehicle, or the device, comprises sensing means arranged to collect sensor data, the processor being arranged to select a portion of the sensor data to be transmitted between the first and second transceivers dependent upon the value of the metric.

41. A vehicle, or a device, according to claim 40 wherein the processor is arranged to store some, or all, of the sensor data upon a local data storage device.

42. A vehicle, or a device, according to any one of claims 34 to 41 wherein content arranged to be displayed upon a browser at a user interface device is stored on a data storage device local to the vehicle and is transmitted selectively via the communications channel to the user interface device.

43. A dynamically configurable processor arranged to be reconfigured to vary a rate of data transfer via a data communications channel in response to an input indicative of the available bandwidth of the communications channel.

44. A processor according to claim 43 wherein the processor is arranged to derive a metric indicative of the available bandwidth from the input and is further arranged to configure the process dependent upon the value of the metric.

45. A processor according to either claim 43 or claim 44 wherein a configuration of the processor is selected from a library of possible configurations stored on a data storage device associated with the processor dependent upon the value of the metric.

46. A processor according to any one of claims 43 to 45 wherein the processor is arranged to output data selectively via a wireless transceiver of a vehicle, or a device, the output data being selected dependent upon the available bandwidth of the communications channel.

47. A method of extending the range of wireless communications between a remote vehicle, or a device, and a base station comprising varying a rate of data transfer over a communications channel between respective transceivers associated with the vehicle and the base station in response to a metric indicative of the quality of the communications channel.

48. The method of claim 46 further comprising establishing a further communications channel with a second base station remote from the vehicle such that the quality of the communications channel between the second base station and the vehicle improves in opposition to the quality of the communications channel between the first base station and the vehicle.